Modeling nitrate-nitrogen removal process in first-flush reactor for stormwater treatment

Area of Science:

• Environmental Engineering
• Water Quality Management
• Wastewater Treatment Technologies

Background:

• Stormwater runoff is a primary source of non-point water pollution, impacting rivers, lakes, and coastal areas.
• Existing best management practices (BMPs) do not specifically address the first-flush period, when most pollutants are discharged.
• Nitrate-nitrogen is a significant pollutant in urban stormwater runoff.

Purpose of the Study:

• To introduce a novel best management practice (BMP) device, the first-flush reactor (FFR), for urban stormwater treatment.
• To develop and present a numerical model, the VART-DN model, for simulating denitrification in the FFR.
• To evaluate the efficacy of the FFR and the VART-DN model in treating highway and urban stormwater runoff.

Main Methods:

• Development of the Variable Residence Time-Denitrification (VART-DN) model to simulate denitrification processes.
• Numerical modeling of the first-flush reactor (FFR) focusing on denitrification mechanisms.
• Sensitivity analysis of VART-DN model parameters to identify key factors influencing denitrification.
• Validation of the VART-DN model using laboratory experimental data from highway stormwater and secondary wastewater.

Main Results:

• The VART-DN model accurately simulates denitrification in the FFR, with simulation errors less than 9.0% for highway stormwater.
• Sensitivity analysis identified key parameters affecting denitrification, including temperature correction factor and maximum nitrate-nitrogen decay rate.
• The model demonstrated good agreement with observed data for both highway stormwater and secondary wastewater, with an R-squared of 0.6912 for wastewater.

Conclusions:

• The developed first-flush reactor (FFR) is a promising novel BMP for urban stormwater treatment.
• The VART-DN model effectively simulates the denitrification process within the FFR, proving its efficacy.
• This approach offers a targeted solution for mitigating water pollution from the critical first-flush stormwater discharge.